I have created a additional forum just like this one
1. General Development Discussion, and another one
2. Not So General Development Discussion

and this results in title as "General Development Discussion - Development Discussion Board" &
" Not So General Development Discussion - Development Discussion Board"
I need to change the title to "General Development Discussion - abc, xyz, 123, Development Discussion Board"
"Not So General Development Discussion - abc, xyz, 123, Development Discussion Board"

How this can be achieved. I am willing to hard code the file. I was able to remove the index page issue using hard coding but not able to find solution to this particular problem.

You have posted on Area51, which is our development board for discussion about the development of new versions of phpBB.
For general support questions, like the one you've posted, please go to https://phpbb.com/community